Triazoles and derivatives thereof are well-known agents to prevent discoloration of copper and copper alloys. Such compounds, arranged for use in electronic materials, include an acidic solution to prevent copper discoloration proposed by the present applicants, which contains 5-methyl-1H-benzotriazole, 5,6-dimethyl-1H-benzotriazole, or 2-mercaptopyrimidine (Patent Document 1 (Japanese Patent Publication No. H04-160173)). Although the compounds have excellent moisture resistance and effectively prevent copper discoloration during storage of treated products, they are susceptible to heat, which is problematic in that copper is oxidized by heating and this results in the oxide film peeling. The present applicants solved this problem in the application of Patent Document 2 (Japanese Patent No. 3373356), which is a solution to prevent copper discoloration obtained by adding a metal more noble than copper, or a salt thereof, to a solution of a heterocyclic compound containing nitrogen and/or sulfur in the molecule and acting as an inhibitor of copper. However, this surface-treating agent, though avoiding the peeling of the oxidized film, does not prevent copper oxidation upon heating.
Substances to suppress copper oxidation during heating and to improve solder wettability include, for instance, a benzimidazole modified at the 2-position (Patent Document 3 (Japanese Patent No. 2575242), Patent Document 4 (Japanese Patent No. 2686168)), or an imidazole derivative (Patent Document 5 (Japanese Patent Publication No. H04-206681), Patent Document 6 (Japanese Patent Publication No. H07-243053)). However, these involve thick films of several tenths of microns to several microns, which have therefore low adhesiveness to resins. To solve this problem, Non-Patent Document 1 (Journal of Technical Disclosure No. 2003-502332) suggests a mercaptobenzoxazole derivative and a mercaptobenzothiazole derivative as a surface-treating agent.
Surface-treating agents containing a tetrazole compound have also been proposed. For instance, Patent Document 7 (Japanese Patent No. 3141145) proposes a tetrazole-based compound, Patent Document 8 (Japanese Patent Publication No. 2000-282033) proposes a surface treating agent comprising a tetrazole-based compound and a thiadiazole-based compound, Patent Document 9 (Japanese Patent Publication No. 2003-3283) proposes roughening a copper surface by a surface-treating agent containing hydrogen peroxide, mineral acid, tetrazole compound, silver ion, and halogen ion, in order to increase the adhesiveness to resins. The present applicants have proposed a surface-treating agent containing a tetrazole compound and a halogen compound (Patent Document 10 (Japanese Patent Application No. 2003-290346)).
Patent Document 1: Japanese Patent Publication No. H04-160173
Patent Document 2: Japanese Patent No. 3373356
Patent Document 3: Japanese Patent No. 2575242
Patent Document 4: Japanese Patent No. 2686168
Patent Document 5: Japanese Patent Publication No. H04-206681
Patent Document 6: Japanese Patent Publication No. H07-243053
Patent Document 7: Japanese Patent No. 3141145
Patent Document 8: Japanese Patent Publication No. 2000-282033
Patent Document 9: Japanese Patent Publication No. 2003-3283
Patent Document 10: Japanese Patent Application No. 2003-290346
Non-Patent Document 1: Journal of Technical Disclosure No. 2003-502332